The nation as a whole has moved slightly to the left

[T]he nation as a whole has moved slightly to the left over the past 20 years, mostly because of a broad societal shift toward acceptance of homosexuality and more positive views of immigrants. Twenty years ago, these two issues created significant cleavages within the Democratic Party, as many otherwise liberal Democrats expressed more conservative values in these realms. But today, as divisions over these issues have diminished on the left, they have emerged on the right, with a subset of otherwise conservative Republicans expressing more liberal values on these social issues.